Impact of Blade Flexibility on Wind Turbine Loads and Pitch Settings

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Xiaocheng Zhu ◽  
Jinge Chen ◽  
Xin Shen ◽  
Zhaohui Du
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Degrees Of Freedom ◽  
Turbine Blades ◽  
Beam Theory ◽  
Nonlinear Effects ◽  
Wind Turbine Blades ◽  
Aerodynamic Loads ◽  
Wind Speeds ◽  
Geometrically Exact Beam

Along with the upscaling tendency, lighter and so more flexible wind turbine blades are introduced for reducing material and manufacturing costs. The flexible blade deforms under aerodynamic loads and in turn affects the flow field, arising the aeroelastic problems. In this paper, the impacts of blade flexibility on the wind turbine loads, power production, and pitch actions are discussed. An advanced aeroelastic model is developed for the study. A free wake vortex lattice model instead of the traditionally used blade element momentum (BEM) method is used to calculate the aerodynamic loads, and a geometrically exact beam theory is adopted to compute the blade structural dynamics. The flap, lead-lag bending, and torsion degrees-of-freedom (DOFs) are all included and nonlinear effects due to large deflections are considered. The National Renewable Energy Laboratory (NREL) 5 MW reference wind turbine is analyzed. It is found that the blade torsion deformations are significantly affected by both the aerodynamic torsion moment and the sectional aerodynamic center offset with respect to the blade elastic axis. Simulation results further show that the largest bending deflection of the blade occurs at the rated wind speed, while the torsion deformation in toward-feather direction continuously increases along with the above-rated wind speed. A significant reduction of the rotor power is observed especially at large wind speed when considering the blade flexibility, which is proved mainly due to the blade torsion deformations instead of the pure-bending deflections. Lower pitch angle settings are found required to maintain the constant rotor power at above-rated wind speeds.

Impact of Blade Flexibility on Wind Turbine Loads and Pitch Settings

2018 ◽  
Author(s):  
Jinge Chen ◽  
Xin Shen ◽  
Xiaocheng Zhu ◽  
Zhaohui Du
Keyword(s):  
Wind Turbine ◽  
Aerodynamic Force ◽  
Turbine Blades ◽  
Beam Theory ◽  
Power Production ◽  
Aerodynamic Loads ◽  
Operational Conditions ◽  
Wind Speeds ◽  
Geometrically Exact Beam ◽  
The Impact

Along with the upscaling tendency, lighter and so more flexible wind turbine blades are introduced for reducing cost of manufacture and materials. The flexible blade deforms under aerodynamic loads and in turn affects the flow field, arising the aero-elastic problems. In this paper, the impact of blade flexibility on the wind turbine loads, power production, and pitch actions is discussed. An aeroelastic model is developed for the study. A free wake vortex lattice model is used to calculate the aerodynamic loads, and a geometrically exact beam theory is adopted to compute the structural dynamics of the blade. The flap, lead-lag bending and torsion DOFs are all included and nonlinear effects due to large deflections are considered. The NREL 5MW reference wind turbine is analyzed. Influences of pure-bending and bending-torsion deformations of the blade on aerodynamic loads are compared. The aerodynamic force distributions under various wind speeds for rigid and flexible blades are also compared. The steady state deformations across the operational conditions are calculated, along with the rotor power production. Significant reduction of power is seen especially under large wind speeds, due to the blade twist deformations under torsion moments. Lower pitch angle settings should be applied to maintain the constant power.

Optimal Design of Horizontal Axis Wind Turbine Blades

2008 ◽  
Author(s):  
Ohad Gur ◽  
Aviv Rosen
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Design Method ◽  
Turbine Blades ◽  
Horizontal Axis ◽  
Optimization Strategy ◽  
Wind Turbine Blades ◽  
Horizontal Axis Wind Turbine ◽  
Wind Speeds ◽  
Design Variables

The optimal aerodynamic design of Horizontal Axis Wind Turbine (HAWT) is investigated. The Blade-element/Momentum model is used for the aerodynamic analysis. In the first part of the paper a simple design method is derived, where the turbine blade is optimized for operation at a specific wind speed. Results of this simple optimization are presented and discussed. Besides being optimized for operation at a specific wind speed, without considering operation at other wind speeds, the simple model is also limited in the choice of design goals (cost functions), design variables and constraints. In the second part of the paper a comprehensive design method that is based on a mixed numerical optimization strategy, is presented. This method can handle almost any combination of: design goal, design variables, and constraints. Results of this method are presented, compared with the results of the simple optimization, and discussed.

The Determination of Stochastic Loads on Horizontal Axis Wind Turbine Blades

1998 ◽  
Vol 120 (2) ◽  
pp. 115-120
Author(s):  
L. N. Freeman ◽  
R. E. Wilson
Keyword(s):  
Wind Turbine ◽  
Test Data ◽  
Degrees Of Freedom ◽  
Turbine Blades ◽  
Horizontal Axis ◽  
Wind Turbine Blades ◽  
Horizontal Axis Wind Turbine ◽  
Wind Speeds ◽  
Power Spectral ◽  
Rainflow Counting

The FAST Code which is capable of determining structural loads of a flexible, teetering, horizontal axis wind turbine is described and comparisons of calculated loads with test data are given at two wind speeds for the ESI-80. The FAST Code models a two-bladed HAWT with degrees-of-freedom for blade bending, teeter, drive train flexibility, yaw, and windwise and crosswind tower motion. The code allows blade dimensions, stiffnesses, and weights to differ and the code models tower shadow, wind shear, and turbulence. Additionally, dynamic stall is included as are delta-3 and an underslung rotor. Load comparisons are made with ESI-80 test data in the form of power spectral density, rainflow counting, occurrence histograms, and azimuth averaged bin plots. It is concluded that agreement between the FAST Code and test results is good.

scholarly journals Separated Pitch Control at Tip: Innovative Blade Design Explorations for Large MW Wind Turbine Blades

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Ranjeet Agarwala ◽  
Paul I. Ro
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Turbine Blades ◽  
Wind Turbine Blades ◽  
Pitch Control ◽  
Wind Speeds ◽  
Extreme Wind ◽  
Blade Tip ◽  
Low Wind Speeds ◽  
Extreme Wind Speeds

This paper focuses on the deployment and evaluation of a separated pitch control at blade tip (SePCaT) control strategy for large megawatt (MW) wind turbine blade and explorations of innovative blade designs as a result of such deployment. SePCaT configurations varied from five to thirty percent of the blade length in 5 percentage increments (SePCaT5, SePCaT10, SePCaT15, SePCaT20, SePCaT25, and SePCaT30) are evaluated by comparing them to aerodynamical responses of the traditional blade. For low, moderate, high, and extreme wind speed variations treated as 10, 20, 30, and 40 percent of reference wind speeds, rotor power abatement in region 3 of the wind speed power curve is realized by feathering full length blade by 6, 9, 12, and 14 degrees, respectively. Feathering SePCaT30, SePCaT25, SePCaT20, and SePCaT15 by 14, 16, 26, and 30 degrees, respectively, achieves the same power abatement results when compared to traditional blade at low wind speeds. Feathering SePCaT30, SePCaT25, and SePCaT20 by 18, 26, and 30 degrees on the other hand has the same effect at high wind speeds. SePCaT30 feathered to 26 and 30 degrees has the same abatement effects when compared to traditional blade at high and extreme wind speeds.

Evaluation of the influence of wind speed and angle of attack on the aerodynamic effect of wind turbine blades

2017 ◽  
Author(s):  
Salete Alves ◽  
Luiz Guilherme Vieira Meira de Souza ◽  
Edália Azevedo de Faria ◽  
Maria Thereza dos Santos Silva ◽  
Ranaildo Silva
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Turbine Blades ◽  
Angle Of Attack ◽  
Wind Turbine Blades ◽  
Aerodynamic Effect

scholarly journals Analysis of Wind Turbine Aging through Operation Data Calibrated by LiDAR Measurement

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2319
Author(s):  
Hyun-Goo Kim ◽  
Jin-Young Kim
Keyword(s):  
Power Generation ◽  
Wind Speed ◽  
Wind Turbine ◽  
Wind Farm ◽  
Free Stream ◽  
Turbine Blades ◽  
Wind Farms ◽  
Lidar Measurement ◽  
Wind Turbine Blades ◽  
Wake Effect

This study analyzed the performance decline of wind turbine with age using the SCADA (Supervisory Control And Data Acquisition) data and the short-term in situ LiDAR (Light Detection and Ranging) measurements taken at the Shinan wind farm located on the coast of Bigeumdo Island in the southwestern sea of South Korea. Existing methods have generally attempted to estimate performance aging through long-term trend analysis of a normalized capacity factor in which wind speed variability is calibrated. However, this study proposes a new method using SCADA data for wind farms whose total operation period is short (less than a decade). That is, the trend of power output deficit between predicted and actual power generation was analyzed in order to estimate performance aging, wherein a theoretically predicted level of power generation was calculated by substituting a free stream wind speed projecting to a wind turbine into its power curve. To calibrate a distorted wind speed measurement in a nacelle anemometer caused by the wake effect resulting from the rotation of wind-turbine blades and the shape of the nacelle, the free stream wind speed was measured using LiDAR remote sensing as the reference data; and the nacelle transfer function, which converts nacelle wind speed into free stream wind speed, was derived. A four-year analysis of the Shinan wind farm showed that the rate of performance aging of the wind turbines was estimated to be −0.52%p/year.

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